1. Field of Invention
The present invention relates to an optical pickup head, and more particularly to a miniature optical pickup head fabricated by using the microelectromechanical technology.
2. Related Art
In recent years, with the development of the semiconductor technology, the microelectromechanical systems (MEMS) technology has many important developments. For an optical data storage system, the micro-opto-electro-mechanical (MOEM) technology provides a good method of fabricating a smaller and lighter optical data storage system.
The MEMS technology is to fabricate integrated miniature semiconductors, which combines multiple technical fields such as optics, mechanics, electronics, and material. The application range of the technology is very wide, including related industries such as opto-electronics, information, communication, and biomedicine. By utilizing the technologies, products can become miniature, and performance, quality, reliability, and added values thereof are improved, and at the same time the fabrication cost is reduced.
In a micro-optical system, a micro-optical element is integrated on a single chip, so a light beam can travel in a free space inside a miniature system. Therefore, the micro-optical system is widely applied in various opto-electronics fields. For example, when the micro-optical system is applied in an optical storage system, as the miniature optical pickup head has important influences on the whole system, when the weight and volume are smaller, the read speed can be increased.
FIG. 1 is a schematic architectural view of a conventional miniature optical pickup head. An optical pickup head 10 is a miniature optical pickup head implemented by utilizing a microelectromechanical technology, which is formed of a plurality of three-dimensional micro-optical elements. Main members of the miniature optical pickup head 10 include: a laser diode (LD) 14, adhered on a silicon (Si) substrate 17 and having a function of emitting a light source, in which a wavelength of the LD 14 is between 350 nm and 800 nm; a beam splitter 11, for separating an energy of a light beam, so that a part of light energy is reflected, and a part of light energy penetrates; a Fresnel lens 12, for making incident light beams parallel; a 45-degree tilted reflector 13, for reflecting an incident light; an objective lens 19, for focusing the incident light beams; and a Fresnel lens 15, for focusing the incident light. The beam splitter 11, and the Fresnel lenses 12 and 15 and the 45-degree tilted reflector 13 are all fabricated through the microelectromechanical technology.
An actuation principle of the optical pickup head 10 is as follows: when the optical pickup head 10 performs writing, a light emitted by the LD 14 penetrates the beam splitter 11, and then light beams are made parallel by the Fresnel lens 12, and the light is reflected by the 45-degree tilted reflector 13 and is focused on a surface of an optical disk 20 through the objective lens 19, so that data is written on the surface of the optical disk 20. When the optical pickup head 10 performs reading, a light emitted by the LD 14 penetrates the beam splitter 11 and light beams are made parallel by the Fresnel lens 12, and the light is reflected onto the surface of the optical disk 20 by the 45-degree tilted reflector 13 and the objective lens 19, and a signal reflected back from the optical disk 20 is focused by the Fresnel lens 12 and then reflected to the Fresnel lens 15 by the beam splitter 11, and is refracted and focused by the Fresnel lens 15 at the optical sensor element 16 on a surface of the silicon substrate 17 to be converted into an electrical signal for output.
However, in the optical pickup head 10, the beam splitter 11 and the Fresnel lenses 12 and 15 occupy a large layout area, so all elements cannot be arranged in a straight zone, and a relatively large area is required. Besides, the objective lens 19 also needs to be arranged additionally, so the optical pickup head 10 has a certain thickness. Therefore, the miniaturization of the optical pickup head 10 is limited, and an optical path of the optical pickup head 10 also cannot be shortened, which is not in line with the cost consideration and efficiency of the system.